Over a number of years the following types of chain tensioning devices have been tested on prototype all terrain vehicles. The resulting observations have led to the development of my invention.
Type 1
Adjustable, but fixed in place tensioning arm devices are best suited for non-reversing industrial applications and bear against the unloaded side of a chain.
Typically, the arm with its slider or idler sprocket is adjusted to remove most of the chain slack and is locked in place. The tensioning device would be adjusted to compensate for wear as required.
This is not suited for use in an all terrain vehicle application, in that if the chain slack is adjusted out to eliminate chain slap, the chain becomes excessively tight as it warms up. This tightness creates wear and excessive tension on chains, sprockets and bearings. If the chain is left slack, it suffers sudden take-up loading when exposed to reversing loads. The abrupt take-up further stretches chains.
Type 2
When using self-adjusting heavy-spring tensioning devices it was found that for reversing load applications the required heavy springs exert a high pre-load force against the chain. These heavy-spring tensioning devices failed when used in an all terrain vehicle application, as they are heavy in weight, difficult to install and service. They have a high pre-load force creating noise and wear on chains, sprockets and bearings.
Type 3
The “Rosta”™ type tensioning devices employ rubber elements which are compressed within a section of square metal tube surrounding their arm pivot bolts. The bolts are cam shaped to compress the rubber elements within the square tube as the arm rotates approximately 45 degrees.
These tensioning devices are not suited for moderate or heavy duty reverse loading applications because the force on the rubber element is leveraged by the length of the arm from the slider or sprocket to the rubber element. The excessive force causes even moderate sized rubber elements to fail. Also the Rosta™ tensioning device is heavier, difficult to adjust in confined space and costly.
Type 4
The technology known in hydraulic damper type tensioning devices found in combustion engines to control slack in timing belts and chains could be used, however, they would be heavier, complex and costly.